Wire Rope Characteristics

Characteristics of Wire

Metal wires can also be made into rope, and is typically either galvanized for protection from water (and subsequent rust) or is stainless steel containing a higher content of nickel to resist rust (it is slightly weaker than galvanized and much more expensive). It is much stiffer than synthetic rope and knots cannot be tied into it without greatly weakening the material from the hard bends required. Because of these unique characteristics, it is useful to study wire as a separate subject from natural and synthetic cordage.

Measuring Wire Rope

Wire rope is separated into a number of classes, such as 6×37 and 6×19. The first number indicates the number of strands, whereas the second number indicates the number of wires in each strand. Because this is separate from the measurement of the wire’s diameter, 6×37 must have smaller individual wires than 6×19 to match the designated composition without adding to the bulk of the wire. Advantages of having more wires-per-strand include greater flexibility for applications that require coiling or reeving. Disadvantages include less resistance to corrosion and greater expense. For the greatest flexibility there is a six-strand composite rope made up of alternate fiber and wire strands around a fiber core, this is called spring lay.

Using calipers, wire rope should then be measured at its widest diameter. The sum of the class and diameter is how the rope is referred to, such as 6×19 1-1/2” galvanized steel.

Serving

An old technique not likely to be observed is called serving. This is the process of covering wire rope (or manila or hemp) standing rigging with a protective layer of smaller stranded tarred manila, known as marline. This would then in turn be slushed with pitch tar to form a weatherproof seal. A serving mallet, a specially designed tool, would be used to apply the serving.

Galvanizing

A powder top coating known as galvanization provides a protective layer between the steel and the marine environment, resisting corrosion and rust. This replaced the need for serving wire. Galvanized wire is suitable for remaining in the weather for extended periods of time and serves well for standing rigging such as stays, guys, or shrouds. It is also suitable for mooring applications. It is not suitable for protecting wire rope used for cargo runners or similar applications where the wire must run through blocks, pulleys, and sheaves.

Splicing

An old but handsome method of splicing an eye into wire is called the Liverpool eye splice. It requires the use of a wire vice—called a rigger’s screw— fa marlingspike, a metal thimble, and a sturdy pair of leather gloves. The thimble is captured by the wire during the splice and takes the chafe of future loads, adding to the strength of the finished product.

This is a good choice for standing rigging. Because of the lay of the wire and how the tucks are made, this is not a good splice for any form of running rigging or cargo operations. If the eye is twisted the strands may open, causing the splice to fail.

A splice acceptable for cargo use is not unlike a regular three-strand splice made in natural or synthetic rope. This involves three tucks with whole strands and two tucks with ½ the wire cut from the tucking strands. It is permissible to use this splice for cargo work.

Interestingly, the only short splice acceptable for cargo use is with wire rope, not with synthetic or natural materials. It is accomplished using the same method as with other constructions of rope.

Socket Eyes

Another method of forming an eye in wire is the use of a Spelter socket. This is a solid fitting with a hole in one end, through which a wire passes, and a hollow cone area where the wire’s strands may be “broomed” open. The opened strands are then etched with acid. A crucible is then used to melt ingots of zinc. This molten zinc is transferred to the socket with a ladle and poured over the separated wires, cooling into a solid and permanent cone. This is typically seen in construction applications. There is no substitution for zinc.

Wire Clips

A useful technique for forming a temporary eye or installing a thimble for the purposes of shackling hooks to the end of a wire is through the use of wire clips. Wrap the wire around the thimble and use a minimum of three clips. There is an old adage for applying wire clips for temporary eye splices in wire rope, “never saddle a dead horse.”

At first this may seem cryptic. Upon examination rope clips (also called bulldogs or Crosby clamps) are made of a u-bolt, two nuts, and an interlocking saddle component. Place the u-bolt over the dead or bitter end and the saddle over the standing part. This protects the stress bearing end of the wire rope from being crushed by the force of the two nuts applied to the u-bolt, locking it into position and crimping down on the strands. Use a minimum of three clips; use five for towing hawsers. This will hold roughly 80% of the original strength of the wire.

Coiling Wire

Due to how wire holds tension kinking can easily result while coiling. If this happens take a turn under, not unlike a half hitch. If this happens repeatedly while coiling reconsider how you are going about the process.

Chain Stopper

To make it fast to the side of the vessel, or hoist an end of it by crane, a chain stopper may be used. This is sometimes called an “endless chain” or just a chain; it is a circular length of chain with no end or termination. It can be passed around an end of the wire several times and hitched through itself and grip a wire very satisfactorily. Only chain can be used as a stopper for wire.

Cleating Wire

Wire has a much larger bending radius than many other materials. Additional care must be taken when manipulating or securing it. Whether securing to a set of horns with an opening in the middle (a cleat), or to bitts, it is good practice to take a minimum of three round turns with the wire before forming figure eights. Each turn provides greater control for the subsequent turn, and this relieves the amount of force exerted on the tighter radius figure eights.

Cutting Wire

Because of the tension inherent in steel, wire rope will want to fly apart and may cause injury when it is parted or cut. Wires shaped to conform to the curvature of the finished rope before the strands are laid up is called preformed, but even these will want to open up.

To accomplish this, three seizings should be placed on either side of the planned cut. These seizings should be made tightly and of steel wire, and act to maintain the original balance of the tension in the wires and strands.

Care for Wire

Sluicing wire, also called slushing, is the lubrication of wire rope with a light oil or mixture of oil and diesel for thinning purposes. It penetrates the outer strands of wire into the core reducing internal friction within the wire, reduces chafe, prevents internal and external rust and corrosion, and overall increases its useful service life.

Care should be taken not to operate winches too quickly. If the weight comes off of the wire it may overlap itself on the drum, called an override. This will kink the wire, place a great deal of stress on a small point, and shorten the wire rope’s life. Sheaves and drums should be at least 20-times the diameter of the wire due to the great bending radius of this material.

While steel does not rot in the traditional sense it definitely rusts. Wire requires a greater degree of care than hemp or manila lines, weighs more, but will provide greater resistance to chafe in applications where this is important.

Qualifying Wire Rope

Aside from the possibility of immediate failure, over straining wire will weaken it. Wire rope will show a decrease in diameter where previous great strain has occurred. Quality control also demands that, when purchased, the supplied wire must meet minimum cross-sectional measurements.

Wire should be condemned if the outside wires are reduced to one-half their original diameter, as well as if opening the strands of the wire with a marlingspike reveals internal corrosion or rust.